Air depolarized electrochemical button cell

ABSTRACT

Cathode cans for use in air depolarized cells, and cells made with such cans. The side wall is stronger than the bottom wall, and has a smoother outwardly-disposed surface than the respective bottom wall surface. Strength, and thus hardness, of the side wall relates to strength, and thus hardness, of the bottom wall, as hardness of 130-185 relates, to hardness of 93-117, on the Vickers scale. Preferred hardness of the side wall is about 130 to 185; and of the bottom wall is about 93 to 117. The side wall is drawn, and an outwardly-disposed surface of the side wall is ironed. As ironed, the surface finish is related to surface finish of the bottom wall, at the same stage, as surface finish R A  of less than 2, preferably about 0.5 to about 1.5, microinches, is related to surface finish R A  of about 2 to about 5, preferably about 2.5 to about 4.5, microinches. Thickness of the side wall is generally up to about 85 percent as great as thickness of the bottom wall. In methods of forming cathode cans in a metal strip, a die has an initializing land, an inner side wall, a cavity inwardly of the inner side wall, and a lip between the initializing land and the inner side wall. Ratio of outer radius of the lip to inner radius of the lip is about 2/1 to about 8/1. Ratio of clearance between punch and die to thickness of the metal strip is about 0.5/1 to about 0.85/1, whereby moving the punch and metal strip into the cavity draws the metal, and irons the outer surface of the metal.

FIELD OF THE INVENTION

[0001] This invention relates to air depolarized alkalineelectrochemical cells. Typically, such cells have metal-containing anodematerials, and air cathodes, and are commonly known as metal-air cells.More particularly, this invention relates to the composition andstructure of cathode cans utilized in such cells, and in general to thecells, themselves. The invention addresses the efficiency of use of thethree-dimensional volume available, in electrical appliances, for use bysuch cells. The invention particularly addresses efficient use ofnon-reactive e.g. structural material in preserving as much space aspossible for occupation by the electrochemically reactive anode materialused by the cell for generating electrical energy. Increased efficiencyof use of non-reactive material provides an increase in the fraction ofthe overall volume of the cell which can be allocated to, or occupiedby, the electrochemically reactive anode material.

BACKGROUND

[0002] The growth in use of small electrically-powered devices hasincreased the demand for very small metal-air electrochemical cells.Metal-air cells have gained significant popularity because only theanode reaction material need be packaged in the cell. In combination,the cathode reaction material is oxygen, which is drawn from thesurrounding ambient environment.

[0003] Such small cells are usually disc-like or pellet-like inappearance, and are about the size of garment buttons. These cellsgenerally have diameters ranging from less than 5.8 millimeters to about25 millimeters, and heights ranging from less than 2.0 millimeters up toabout 15 millimeters. The small size of such cells, and the limitedamount of electrochemically reactive material which can be contained insuch small metal-air cells, result in a need for improving theefficiency and completeness of the electrochemical reactions, which areused in such cells for generating electrical energy, and for improvingthe fraction of the overall volume of such cell which can be occupied bythe electroactive anode material.

[0004] Such metal-air cells take in atmospheric oxygen, and convert theoxygen to hydroxyl ions in the air cathode by interaction with aqueousalkaline electrolyte. The hydroxyl ions then migrate to the anode, wherethey cause the metal contained in the anode to oxidize. Usually theactive anode material in such cells comprises zinc, although a varietyof other operable anode materials are well known to those skilled in theart.

[0005] More particularly, the desired reaction in the air cathode of ametal-air cell involves the reduction of oxygen, the consumption ofelectrons, and the production of hydroxyl ions. The hydroxyl ionsmigrate through the aqueous alkaline electrolyte toward the anode, whereoxidation occurs, forming zinc oxide.

[0006] In typical metal-air cells, air enters the cell through one ormore air ports in the bottom the cathode can. The port or ports extendthrough the bottom wall of the cathode can, and may be immediatelyadjacent the cathode assembly, or may preferably be separated from thecathode assembly by an air reservoir, which is typically occupied by anair diffusion member.

[0007] In such arrangements, the port facilitates movement of airthrough the bottom of the cathode can and to the cathode assembly. Atthe cathode assembly, the oxygen in the air reacts with water as achemically reactive participant in the electrochemical reaction of thecell, and thereby forms the hydroxyl ions.

[0008] Since the overall electrochemical capacity of any electrochemicalcell is to some extent determined by the quantity of electrochemicallyreactive materials which can be loaded into the cell, it is important tomaximize, in the cell, the size of the cavity which is devoted tocontaining the electrochemically reactive materials. In the case of ametal-air cell, contained reactive material is limited to the anodematerial.

[0009] In general, the size of any given cell is limited by the insidedimensions of the space provided in the article, namely the appliance,in which the cell will operate. For example, the size of a hearing aidcell is limited to the internal dimensions of the space, provided forthe cell, in the hearing aid appliance. The internal dimensions of thespace are determined by the hearing aid manufacturer, not the power cellmanufacturer.

[0010] Thus, any given appliance includes a limited amount of grossspace or volume allotted to occupancy by the electrochemical cell whichpowers the appliance. That gross space may ultimately be dividedaccording to four functions, all competing for portions of the grossspace. A first portion of the space is used to provide clearance betweenthe interior elements of the space and the exterior elements of theelectrochemical cell.

[0011] A second portion of the space is occupied by the structural andotherwise non-reactive elements of the electrochemical cell.

[0012] A third portion of the space is allocated for occupation by theelectrochemically reactive material in the electrochemical cell, and, ina metal-air cell, especially the anode material.

[0013] Finally, a fourth portion of the space, as appropriate, cansometimes be described as “wasted” space, because it serves none of theabove first through third functions. Such wasted space is typicallyfound outside the cell, e.g. at corner locations, where the corner ofthe cell is less square than is structurally feasible, thereby wastingvolume that potentially might be occupied, either directly or indirectlyby electrochemically reactive material. Such wasted space might also beconsidered to be included in the space allocated to clearance becausesuch space is typically located outside the cell.

[0014] Any increase in the third portion of the space, namely the cavityin the anode can which cavity is allocated to the anode material, isnecessarily gained at the expense of one or more of the other threeportions of the fixed volume allocated for occupation by the cell,namely the first clearance portion, the second portion devoted to thenon-reactive elements of the cell, or any fourth waste portion. Thus, itis important to identify the first, second, and fourth portions of theoverall space, and, where possible, to reduce the amount of spacedevoted to such uses. To the extent such uses can be reduced, the spaceso recovered can, in general, be allocated for use to hold additionalamounts of electrochemically reactive anode material, thereby increasingthe potential overall capacity of the cell to generate electrical energywithin the limited amount of gross space or volume provided, in theappliance, for occupation by the cell.

[0015] Overall cell height and width dimensions are specified by theInternational Electrotechnical Commission (IEC).

[0016] Of the first, second, and fourth portions of the cell, theopportunity for capturing space from the first portion, devoted toclearance, relates in part to the ability of the manufacturer to controlthe range of outer diameters of the cathode cans from which the cellsare made. To the extent the range of diameters can be reduced, nominalclearance may be reduced accordingly.

[0017] It is known that traditional methods of forming cathode cans foruse in hearing aid cells have a tendency to form an outward bulge in thediameter of the cathode can at the intersection of the side wall withthe bottom wall, whereby allowance must be made in the can specificationfor occurrence of such bulge.

[0018] In addition, applicants have concluded that further potential forrecovering space for use in holding anode material, and thus to increasevolume efficiency of the cell, lies primarily in the second portion ofthe cell, namely the structural and otherwise non-reactive elements ofthe cell. These elements generally comprise the cathode can, the anodecan, the seal, and the cathode assembly, these typically representingall of the major structural elements of the cell. Thus, to get morespace from the second portion of the cell, that space must be taken fromthe anode can, the cathode can, the cathode assembly, or the seal, orsome combination of these.

[0019] This invention focuses on apparatus, methods, and materials forproviding improved cathode cans, and wherein the cathode cans havereduced cross-section thicknesses, and reduced range of thicknesses fromcan to can, while maintaining suitable strength parameters to properlysupport the manufacture and use of such cans, and cells made therewith.Such cans typically have a pair of nickel layers, and a steel layerbetween the nickel layers.

[0020] It is known to desire to reduce the thickness of the non-reactivestructural materials of the cell. However, the desire to reduce thethickness of such non-reactive elements operates in tension against therequirement that such structural elements have suitable fabricationproperties, and suitable strength to support the fabrication and use ofthe cell. Accordingly, an element cannot simply be made thinner withoutconsidering the effect such thinning will have on the ability tofabricate the element, or to fabricate and use a cell made therewith.

[0021] Similarly, it is known to select different materials from whichto fabricate the respective non-reactive elements. Such differentmaterials may have different chemical composition, or different chemicalor physical properties. However, changing material selection alsoaffects the ability to fabricate the element, and the ability of theelement to support fabrication and use of the cell.

[0022] Thus, where thinner, or harder, metal strip is contemplated foruse to form cathode cans, there is the prospect of developing cracks inone or more of the layers of the metal strip during conventionalfabrication of the can.

[0023] Accordingly, any change in selection of material from which thecans are to be made, or physical dimensions of such material, must becarefully balanced against the fabrication requirements associated withsuch material as the material is used to fabricate the respectiveelements; as well as the requirements associated with fabrication anduse of a cell utilizing such elements. Any change of material must, ofcourse, be compatible with the chemical operating environment withinwhich the cell operates. Typically, air depolarized cells operate in analkaline environment, and so any material used therein must becompatible with such environment.

[0024] It is an overall object of the invention to provide improved airdepolarized electrochemical button cells.

[0025] It is a more specific object of the invention to provide cathodecans wherein the side walls are harder than the bottom walls.

[0026] It is yet another object to provide cathode cans whereinoutwardly-disposed side walls have smoother finishes than correspondingsurfaces of the respective bottom walls.

[0027] It is still another object to provide can forming systemsincluding a punch and a die wherein the clearance between the punch anddie is less than the thickness of a metal strip to be formedtherebetween.

[0028] Yet another object is to provide methods of making cathode cansin a metal strip, wherein the clearance between the punch and the die isless than the thickness of the metal strip.

[0029] It is a further object to provide cathode cans wherein the sidewall is harder than, and thinner than, the bottom wall, and wherein anoutwardly-disposed surface of the side wall has a smoother finish than acorresponding outwardly-disposed surface of the bottom wall.

SUMMARY OF THE DISCLOSURE

[0030] The invention, in general, comprehends a cathode can, for use inan air depolarized electrochemical cell, the cathode can comprises abottom wall, and a circumferential side wall, extending upwardly from alower edge of the side wall adjacent the bottom wall, and terminating atan upper, distal edge. The side wall has a height generallycorresponding to an overall height of the cathode can of no more thanabout 15 mm, preferably no more than about 8 mm, and a circumferencedefining an overall diameter of the cathode can of no more than about 25mm, preferably no more than about 13 mm. The ratio of the overall heightto the overall diameter of the cathode can is about 0.1/1 to about 1/1.The side wall has a first strength, as measured by hardness, greaterthan a second strength, as measured by hardness, of the bottom wall. Thestrength of the side wall is related to the strength of the side wall asa side wall hardness of about 130 to about 185 Vickers (84-90 on theRockwell Hardness 15T scale) is related to a bottom wall hardness ofabout 93-117 Vickers (77-82 on the Rockwell 15T scale).

[0031] The ratio of the hardness of the side wall to the hardness of thebottom wall, on the Vickers scale, is preferably between about 0.60/1and about 0.85/1.

[0032] Preferred absolute hardness of the side wall is about 130 toabout 185 on the Vickers scale and about 84 to about 90 on the RockwellHardness 15T scale; and preferred hardness of the bottom wall is about93 to about 117 on the Vickers scale and about 77 to about 82 on theRockwell 15T scale.

[0033] The cathode can side wall preferably has an outwardly-disposedironed surface. The outwardly-disposed side wall surface, as ironed,comprises a first surface finish. The bottom wall has a second surfacefinish. The surface finish of the side wall is preferably related to thesurface finish of the bottom wall as a surface finish R_(A) of less than2 microinches is related to a surface finish R_(A) of about 2microinches to about 5 microinches.

[0034] In preferred embodiments, the bottom wall has a first thickness,the side wall having a second thickness no more than about 85 percent asgreat as the thickness of the bottom wall.

[0035] Preferred embodiments of the can comprise first and second layerscomprising nickel, and a layer of steel between the nickel layers, andcan include a metal plating layer on at least one of the nickel layerssuch that the respective nickel layer is between the plating layer andthe steel layer.

[0036] For use in air depolarized electrochemical cells, a respectivecathode can includes at least one air port in the bottom wall.

[0037] The invention further comprehends an air depolarizedelectrochemical button cell having an overall height of no more thanabout 15 mm, preferably no more than about 8 mm, and a circumferencedefining an overall diameter of the cathode can of no more than about 25mm, preferably no more than about 13 mm, the cell comprising an anodeassembly, a cathode including a cathode can having a hardened side wallas described above, a separator, and an electrolyte.

[0038] In a second family of embodiments, the invention comprehends acathode can having a bottom wall, and a circumferential side wall,extending upwardly from the bottom wall. The side wall has a heightgenerally corresponding to an overall height of the cathode can of nomore than about 15 mm, preferably no more than about 8 mm, and acircumference defining an overall diameter of the cathode can of no morethan about 25 mm, preferably no more than about 13 mm. The ratio of theoverall height to the overall diameter of the cathode can is about 0.1/1to about 1/1. The side wall has an outwardly-disposed ironed surface.The side wall surface, as ironed, comprises a first surface finish. Thecorresponding outer surface of the bottom wall has a second surfacefinish. The surface finish of the side wall is related to the surfacefinish of the corresponding outwardly-disposed surface of the bottomwall as a surface finish R_(A) of less than 2 microinches is related toa surface finish R_(A) ranging from about 2 microinches to about 5microinches.

[0039] In some embodiments, the surface finish of the side wall rangesfrom about R_(A) 0.5 microinch to about R_(A) 1.5 microinches and thesurface finish of the bottom wall ranges from about R_(A) 2.5microinches to about 4.5 microinches.

[0040] In preferred embodiments, the cathode can comprises first andsecond layers comprising nickel, and a layer of steel between the nickellayers, and may optionally include a metal plating layer on at least oneof the nickel layers such that the respective nickel layer is betweenthe plating layer and the steel layer; and typically includes at leastone air port in the bottom wall.

[0041] This second family of embodiments further comprehends an airdepolarized electrochemical button cell having an overall height of nomore than about 15 mm, preferably no more than about 8 mm, and acircumference defining an overall diameter of the cathode can of no morethan about 25 mm, preferably no more than about 13 mm, the cellcomprising an anode, a cathode including a cathode can having a surfacefinish as described above, a separator, and an electrolyte.

[0042] A third family of embodiments of the invention comprehends amethod of forming a cathode can from a metal strip having a firstthickness between opposing surfaces thereof, using a punch incombination with a female die. The female die comprises an initializingland, an upstanding inner side wall, a cavity defined inwardly of theinner side wall, and a lip between the initializing land and the innerside wall. The method comprises urging the punch against an element ofthe metal strip and thus urging both the punch and the metal strip intothe cavity in the female die such that the metal strip is disposedbetween a first outer surface of a side wall of the punch, and a secondinner surface of the side wall of the female die. The metal is thusdrawn about the lip of the female die. The lip of the female diecomprises a first outer cross-sectional radius disposed toward theinitializing land, and a second inner cross-sectional radius disposedtoward the inner side wall. The first radius is disposed between thesecond radius and the initializing land. The second radius is smallerthan the first radius and is disposed between the first radius and theinner side wall.

[0043] This embodiment further comprehends moving the punch, and thecorresponding element of the metal strip, into the cavity such that theouter side wall of the punch comes into facing, and thus working,relationship with the inner side wall of the female die. The clearancebetween the respective inner and outer side walls is less than thethickness of the metal strip being drawn therebetween, whereby movementof the punch into the cavity and corresponding drawing of the metalstrip, along with the punch, and into sliding engagement against theinner surface of the side wall, results in rubbing, surface-to-surfaceengagement of an outwardly-disposed surface of the metal strip againstcorresponding portions of the inner surface of the female die, thusdrawing the metal strip, and working the surface of the metal strip,thereby making a cathode can precursor as an integral part of the metalstrip, the cathode can precursor having a bottom wall, and a side wallextending upwardly from the bottom wall.

[0044] This embodiment further comprehends, subsequent to the moving ofthe punch into the cavity, severing the cathode can precursor from themetal strip, thereby to form the cathode can.

[0045] Leading and trailing edges of the element, or workpiece, beingworked are cut transversely across the metal strip before the metalstrip is urged into the die cavity, while retaining attachment of theelement to the metal strip at opposing sides of the strip.

[0046] In general, the moving of the punch into the cavity works themetal strip by both thinning the metal and bending the metal. Suchpreferably cold working of the metal strip at the outwardly-disposedsurface increases the smoothness of the outwardly-disposed surface ofthe metal strip.

[0047] In preferred embodiments, the bottom wall of the cathode canprecursor has a second thickness, and the side wall of the cathode canprecursor has a third thickness, of about 60 percent to no more thanabout 85 percent, preferably about 60 percent to about 80 percent, asgreat as the second thickness.

[0048] In some embodiments, the metal strip comprises first and secondlayers comprising nickel, and a layer of steel between the nickellayers, and can further include the step of post-plating the cathode canwith a plating material, for example and without limitation, nickel,gold, or silver, after the severing of the cathode can precursor fromthe metal strip, whereby the worked, outwardly-disposed surface isplated with the plating material.

[0049] Preferably, the ratio of the second radius to the first radius isabout 2/1 to about 8/1, more preferably about 3/1 to about 6/1, and mostpreferably, about 4/1.

[0050] The ratio of the clearance between the punch and the female dieto the thickness of the metal strip, before any working of the metalstrip in the invention is about 0.5/1 to about 0.85/1.

[0051] The metal strip has a preferred hardness of about 93 to about 117on the Vickers scale prior to being worked in said cavity.

[0052] Preferably, that portion of the metal strip which is worked inthe cavity has a worked hardness of about 130 to about 185 on theVickers scale.

[0053] The invention further comprehends an air depolarizedelectrochemical button cell comprising an anode assembly, a cathodeincluding a cathode can fabricated according to an above-recited method,a separator, and an electrolyte.

[0054] In a fourth set of embodiments, the invention comprehends a canforming system for forming a cathode can having at least one air port ina bottom wall thereof, from a metal strip. The can forming systemcomprises a punch in combination with a female die, and a severingdevice. The female die comprises an initializing land, an upstandinginner side wall extending about a cavity, and a lip between theinitializing land and the inner side wall. The lip of the female diecomprises a first outer cross-sectional radius disposed toward theinitializing land, and a second inner cross-sectional radius disposedtoward the inner side wall. The first radius is between the secondradius and the initializing land. The second radius is smaller than thefirst radius, and is disposed between the first radius and the innerside wall. The severing device severs the cathode can precursor from themetal strip, thereby to form the cathode can.

[0055] The can forming system can further include the metal strip,having a thickness, and being disposed between the punch and the die asthe punch, and the corresponding element of the metal strip, moves intothe cavity such that the outer side wall of the punch comes into facing,and thus working, relationship with the inner side wall of the femaledie. The clearance between respective inner and outer side walls is lessthan the thickness of the metal strip being drawn therebetween. Thus,movement of the punch into the cavity and corresponding drawing of themetal strip, along with the punch, and into sliding engagement againstthe inner surface of the side wall results in rubbing,surface-to-surface engagement of an outwardly-disposed surface of themetal strip against corresponding portions of the inner surface of thefemale die, thus drawing the metal strip and thereby substantiallythinning the metal strip, working the metal strip by both substantialthinning of the metal and bending of the metal. The drawing, working,and corresponding thinning of the metal strip gives theoutwardly-disposed surface of the metal strip a finer surface finish,and makes a cathode can precursor as an integral part of the metalstrip.

[0056] The can forming system commonly includes the metal strip havingfirst and second layers comprising nickel, and a layer of steel betweenthe nickel layers.

[0057] The metal strip preferably has a hardness of about 93 to about117 on the Vickers scale prior to being worked by the can formingsystem.

[0058] In preferred embodiments, that portion of the metal strip whichis worked in the can forming system has a worked hardness of about 130to about 185 on the Vickers scale.

[0059] Typical cathode can made with the above can forming systemcomprises a bottom wall, having at least one air port therein, and acircumferential side wall extending upwardly from the bottom wall, theside wall having a height generally corresponding to an overall heightof the cathode can of no more than about 15 mm, preferably no more thanabout 8 mm, and a circumference defining an overall diameter of thecathode can of no more than about 25 mm, preferably no more than about13 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0060]FIG. 1 shows a representative cross-section of an electrochemicalcell of the invention.

[0061]FIG. 2 shows a representative cross-section of a cathode can ofthe invention.

[0062]FIG. 3 shows an enlarged representative cross-section of the sidewall of the can of FIG. 2, and is taken at the dashed circle labeled 3in FIG. 2.

[0063]FIG. 4 is a block diagram illustrating the overall process ofmaking cathode cans of the invention.

[0064]FIG. 5 shows an elevation, in cross-section, illustrating therelative positioning of the first punch and the first die, at the firstpunch station.

[0065]FIG. 6 shows the punch having moved, along with the metal element,down into the die, thus to draw the metal into the die and to form themetal about the punch.

[0066] The invention is not limited in its application to the details ofconstruction or the arrangement of the components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments or of being practiced or carried out inother various ways. Also, it is to be understood that the terminologyand phraseology employed herein is for purpose of description andillustration and should not be regarded as limiting. Like referencenumerals are used to indicate like components.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0067] Referring now by characters of reference to the drawings, andfirst to FIG. 1, the number 10 refers to an air depolarized button cellof the invention. Cell 10 includes negative electrode 12, also referredto as anode 12. Anode 12 includes an anode can 14 and electrochemicallyreactive anode material 16 contained generally within the anode can.Anode can 14 has a top wall 18, and circumferential downwardly-dependingside wall 20. Top wall 18 and side wall 20 have, in combination, aninner surface 22 and an outer surface 24. Side wall 20 has a height“HAS,” shown in FIG. 1, generally corresponding to the overall height ofthe anode can, and terminates in a distal edge at circumferential anodecan foot 26.

[0068] Positive electrode 30, also referred to as cathode 30, includesan air cathode assembly 32, contained within cathode can 34. Cathode can34 has a bottom wall 36, and a circumferential upstanding side wall 37extending upwardly from the bottom wall. Bottom wall 36 has a generallyflat inner surface 38, a generally flat outer surface 40, and an outerperimeter 42 defined on the flat outer surface 40. Bottom wall 36 has afirst thickness “T1” between inner and outer surfaces 38 and 40.

[0069] As illustrated in FIG. 1, a plurality of air ports 44 extendthrough bottom wall 36 of the cathode can, providing avenues fortransport of oxygen into the cell adjacent cathode assembly 32. Airreservoir 45 spaces cathode assembly 32 from bottom wall 36 and thecorresponding ports 44. A porous diffusion layer 47 extends into airreservoir 45. Circumferential side wall 37 of the cathode can extendsupwardly from bottom wall 36, terminates at distal edge 49, and has aninner surface 46 and an outer surface 48.

[0070] Side wall 37 of the cathode can, as shown in FIG. 1, has a height“HCS1,” generally corresponding to the height of the cathode can inFIG. 1. As seen in FIG. 1, height “HAS” of anode can side wall 20 issignificantly greater than half the height “HCS1” of the cathode canside wall. Outer surface 40 of bottom wall 36 has a substantially flatportion extending radially outwardly to outer perimeter 42, and radiallyoutwardly of inner surface 46 of side wall 20. Side wall 37 has a secondthickness “T2” between inner and outer surfaces 46 and 48.

[0071] Anode 12 is electrically insulated from cathode 30 by sealmaterial illustrated by a seal 50. Seal 50 includes a circumferentialside wall 52 disposed in space 53 which side wall extends over asubstantial portion of height “HAS” between upstanding side wall 37 ofthe cathode can and downwardly-depending side wall 20 of the anode can.A seal foot 54 is disposed generally between foot 26 of the anode canand cathode assembly 32, and a seal top 56 where side wall 52 of seal 50extends from between side walls 20 and 37 adjacent the top of the cell.As illustrated in FIG. 1, the anode, including anode can 14 and anodematerial 16, is received inside the cathode can such that the entiretyof the cathode can side wall 37 is disposed radially outwardly of anodecan side wall 20.

[0072] Outer surface 58 of cell 10 is defined by portions of the outersurface 24 of the top of the anode can, outer surface 48 of side wall 37of the cathode can, outer surface 40 of the bottom wall of the cathodecan, and top 56 of seal 50. Thus, the anode can and the cathode can, incombination, define a top and a bottom of the cell, height “H2” of thecell of no more than about 15 mm, and maximum diameter “W2” of the cellof no more than about 25 mm. The ratio of the maximum height to themaximum diameter ranges from about 0.1 /1 to about 1/1. As seen in FIG.1, height “H2” and maximum diameter “W2” define a right cylinder,representing an overall volume of the cell, generally ranging betweenabout 0.06 cm³ and about 0.60 cm³ for hearing aid applications.

[0073] Inner surfaces of anode can 14, cathode assembly 32, and sealfoot 54, generally define a cavity 28 which contains the anode material16. For efficiency of utilization of the space allocated, in theappliance, for occupation by the power cell, cavity 28 should be aslarge as possible. In general, this invention addresses the materialsand structures which affect the degree of efficiency with which cell 10fills the space, allocated for the power cell in the appliance withinwhich the cell is to be used, with electrochemically reactive materials.Accordingly, the invention addresses materials, structures, and methodsfor improving the efficiency with which cell 10 fills space in theappliance with electrochemically reactive material.

[0074] At cell assembly, closing force is applied to the top and bottomof the cell being assembled. Bottom wall 36 receives a portion of thecell closing force. Such closing force pushes upwardly on the bottomwall, whereby bottom wall 36 tends to be dished upwardly, toward theinterior of the cell being formed. Such upward dishing is undesirablefor a number of reasons, including, without limitation, that suchdishing reduces the usable volume inside the cell, with correspondingreduction in total cell discharge capacity, as well as giving theimpression that the cell has been damaged.

[0075] It is desirable to maintain bottom wall 36 flat, whereby thebottom wall is not dished inwardly at cell closure. The ability of thebottom wall to resist such inward dishing is related to, among otherthings, the thickness of the bottom wall, as well as to the materialfrom which the cathode can is fabricated, and the properties of thematerial used in the bottom wall.

[0076]FIG. 2 illustrates a cathode can 34 after the cathode can is fullyfabricated, and prior to the cathode can being assembled with other cellelements to form an air depolarized button cell. As illustrated in FIGS.1 and 2, thickness “T1” of the bottom wall is greater than thickness“T2” of the side wall. Height “HCS2” of side wall 37 generallycorresponds to the overall height of can 34, and is greater than “HCS1”of the crimped can in FIG. 1.

[0077]FIG. 3 illustrates a typical cross-section of side wall 37. Asillustrated there, a core layer 60 of steel, preferably cold rolledsteel, is disposed between an inner layer 62 of nickel and an outerlayer 64 of nickel. Inner layer 62 defines inner surface 46 of theillustrated side wall 37, and outer layer 64 defines the outer surface48 of the illustrated side wall. In some embodiments, additional layers,for example a post-plated layer of nickel can be used inwardly and/oroutwardly, respectively, of layers 62 and 64. As used herein, “inwardly”and “outwardly” refer to what become inward and outward with respect toa cell when the cathode can is assembled thereinto.

[0078]FIG. 4 is a block diagram representation of the overall process offabricating cathode cans 34 according to the invention. Referring now tospecific processes, and to the blocks representing such processes, agenerally endless strip of metal having the above described three ormore layer structure is fed into a processing line for fabrication ofcathode cans. At step 66, registration holes are formed in the metalstrip, out of the way of forming cathode cans therefrom. At step 68, airports are fabricated in the metal strip in registration with theregistration holes, at locations which will become the bottom walls ofrespective cathode cans made therewith.

[0079] At step 70, leading and trailing edges of workpiece elements,respective pairs of which will define separate cathode cans, are cuttransversely across the metal strip, while retaining attachment of therespective workpiece elements to the metal strip at opposing sides ofthe strip. At the conclusion of the work performed at step 70,individual, generally circular, work piece elements have been defined inthe strip, in registration with the registration holes and the airports, with suitable cuts at each work piece element to allow the workpiece element to be further fabricated into a can. Thus, the work pieceis connected to the continuous metal strip by suitable attachmentribbons (not shown) along the metal strip.

[0080] Step 72 represents the novel first punch step of the inventionwherein the flat work piece element is first fabricated into the shapeof a cup or can, as a cathode can precursor. Punch lubricants are, ofcourse, used in the conventional manner. Step 74 represents the secondpunch step of the invention wherein the cathode can precursor is furtherfabricated to the preferred configuration of cathode cans of theinvention.

[0081] Further finish fabrication such as coining and flaring of the topof the cathode can is performed at step 76. Finally, the completed canis severed from the metal strip at step 78.

[0082] Referring now to FIGS. 5 and 6, and first punch step 72, punch 80is aligned over female die 82. Metal strip 84 is disposed between punch80 and female die 82. Stripper die 86 is disposed about punch 80 so asto strip the work piece off of punch 80 as punch 80 is retracted fromfemale die 82. As illustrated, metal strip 84 has a thickness “T3” of,for example, about 0.15 mm.

[0083] Referring now to FIG. 6, punch 80 has a side wall 92, and abottom wall 94. Side wall 92 has an outer surface 96. Correspondingly,female die 82 has a side wall 98 having an inner surface 100 facingcavity 101. A lip 103 is disposed between initializing land 102 andinner surface 100. Lip 103 includes an outer radius 104, and an innerradius 106 between outer radius 104 and inner surface 100. Asillustrated, inner radius 106 is substantially smaller than outer radius104. The ratio of the outer radius to the inner radius is about 2/1 toabout 8/1. Preferably, the radius is about 3//1 to about 6/1. Theillustrated radius ratio is about 4/1.

[0084] The fabrication process illustrated in FIGS. 5-6 illustratesfabricating a cathode can for a size 312 (PR41) air depolarized buttoncell. In that regard, the outer radius at lip 103 is about 0.75 mm toabout 1.5 mm, and the inner radius is about 0.1 mm to about 0.5 mm. Thediameter “D1” of the outer edge of the outer radius is about 8 mm toabout 10 mm. The inside diameter “D2” of cavity 101, again for a PR41cell, is about 7.68 mm to about 7.76 mm. The outside diameter “D3” ofthe outer surface of punch 80 is about 0.04 mm to about 0.055 mm. lessthan the diameter of the inner surface of the die.

[0085] The clearance “C1” between outer surface 96 of punch 80 and innersurface 100 of cavity 101, which in FIG. 6 corresponds to “T2,” isaccordingly configured to be less than the thickness “T3” of metal strip84 prior to working the metal strip. Namely, clearance “C1” is typicallyabout 65% to about 80%, preferably no more than about 85%, of thethickness of metal strip 84. Accordingly, clearance “C1” between punchand die is about 0.04 mm to about 0.055 mm less than the unworkedthickness of the metal strip.

EXAMPLE

[0086] Referring to FIGS. 5-6, as punch 80 moves toward and into cavity101, bottom wall 94 of the punch engages the top surface of therespective work piece element of metal strip 84, and pushes the workpiece element into cavity 101 ahead of the bottom wall.

[0087] As the punch enters the cavity, the clearance between the outersurface of the punch and the inner surface of side wall 98 of the die isless than the thickness of the metal strip. Accordingly, as the metalstrip is punched into the cavity, the metal strip is necessarilythinned.

[0088] The mechanism for thinning the metal strip is set up by theutilization of the double radius lip 103 which defines the intersectionof initializing land 102 and inner side wall 98. Applicants havediscovered that a single small, or tight, radius as at 106 issatisfactory for creating a desired shape for the can, but risks tearingor cracking the metal being so formed; and that a single larger radiusas at 108 forms without metal failure, but does not create the desiredshape for the can. By contrast, the double radius structure fabricates asatisfactory can shape while satisfactorily attenuating risk of metalfailure during this first punch step 72.

[0089] As the metal is punched into cavity 101, that metal which isjuxtaposed in front of bottom wall 94 is simply pushed ahead of thepunch, without significant change in thickness of the metal. The metalwhich is drawn down along side walls 92, 98 is stretched about lip 103,successfully thinning the metal to a thickness operative to traverse theclearance between the punch and the die, thereby to create the cathodecan precursor by taking the first step in fabricating thethree-dimensional can shape.

[0090] In addition, as punch 80 moves downwardly into cavity 101, outersurface 112 of the metal strip is in sliding, frictional engagementagainst inner surface 100 of side wall 98. Namely, the outer surface ofthe metal strip material is cold-worked by the sliding of the outersurface of the metal strip along the interface of the metal strip withside wall 98 of die 82. In the process, the metal strip is under tensionfrom the leading of bottom wall 94 of the punch, and is simultaneouslyunder the compressive force of side walls 92 and 98 urging thinning ofthe metal strip in order to fit into the clearance between punch and diein cavity 101.

[0091] As the metal strip thus advances into cavity 101, and the outersurface of the metal strip is in sliding engagement with the innersurface of cavity 101, outer surface 112 of the side wall precursor 37Pis worked by side wall 98 of the die. Side wall 98 is, of course, highlypolished in order to properly work metal strip 84 and to impart adesirable polished finish to the side wall. Typical finish on innersurface 98 is less than 2 microinches, whereas typical finish on metalstrip 84 and bottom wall 36P of the can precursor, is greater than 2microinches, such as up to 5 or more microinches.

[0092] Such working of surface 112 accomplishes two results. First, thecold working results in hardening of the metal strip, especially at andadjacent outer surface 112. Second, the cold working against the highlypolished side wall 98 creates a highly polished surface finish on sidewall 112, such that the surface finish of side wall 112 is substantiallysmoother than metal strip 84, and smoother than bottom wall precursor36P. Assuming a surface finish R_(A) of about 2 microinches to about 5microinches for metal strip 84, the resulting surface finish R_(A) of anexemplary side wall 37 is less than 2 microinches, preferably less than1.5 microinches. In highly preferred embodiments, the surface is such asto measure less than 1 microinch. In some embodiments, the finish is sosmooth as to make it difficult to detect any surface finish measurementon an instrument having a sensitivity to R_(A) 0.1 microinch.

[0093] By the end of the punch stroke at step 72, the first punch stephas transformed the flat, disc-like work piece element into a cup or canhaving substantially, though not entirely, the full height “HCS1” of thefinished cathode can of the invention. Namely, the height of the can atthe completion of the first punch stroke is within a few thousandths ofan inch of the finished height “HCS1.”

[0094] Also by the end of the first punch stroke at step 72, the ironingof the outer surface of the side wall, between the punch and the die, isoccurring simultaneously over substantially the full height of the sidewall, from the bottom wall 94 of the punch up to the inner radius 106.

[0095] After completion of the punch stroke illustrated in FIGS. 5 and6, punch 80 is withdrawn, and the can precursor so formed is strippedfrom the punch by stripper die 86. The work piece then moves on tosecond punch step 74. At step 74, the inner diameter of the cavity islarger than at the first step, and the outer diameter of the punch issmaller than punch 80 in the first step. Operation of the second punchtightens the radius of the metal about lip 103, and further forms asharper corner at the joinder of the bottom wall and the side wall ofthe cathode can precursor.

[0096] Accordingly, in the preferred illustrated embodiment of theprocesses of the invention, ironing occurs only in combination withdrawing. Further, in accord with the preferred embodiments, fabricationof substantially the full height of the cathode can is accomplished onlyin combination with steps wherein the punch moves toward the female die.

[0097] Yet further, the step which performs the ironing commences withor from the work piece element in a flat disc-like configuration.

[0098] The hardness and formability of the metal strip representcompromises between the need to form the strip in making the cathode canand the need to crimp the distal edges of side wall 37 in closing thecell at final assembly, and the corresponding desire to obtain as muchstrength as possible from a minimum material thickness.

[0099] A preferred metal strip includes a core layer of cold rolledsteel, plated on opposing surfaces with layers of nickel, each of thelayers being about 0.00165 mm to about 00.215 mm thick. The platedthree-layer structure is preferably but not necessarily diffusionannealed such that the nickel layers are diffusion bonded to the corelayer. The diffusion annealed three-layer strip is then temper rolled tospecified thickness which, in the preferred embodiment herein is about0.15 mm.

[0100] As referred to in TABLE 1 following, and elsewhere herein, unlessnoted otherwise, the nomenclature used for Temper of the metal strip isadapted from the Special Temper designation suggested by supplied ThomasSteel Strip Corporation, Warren, Ohio, USA, from whom such metal stripcan be obtained. The preferred such metal strip is designated Temper “3Special” by Thomas Steel Strip. A similarly desirable material isavailable from Hille & Muller, Dusseldorf, Germany, under the temperdesignation “LG.” Table 1 illustrates properties of a preferred metalstrip having the preferred “3 Special” temper designation, as well as analternative material having a “4” temper designation. Both temper “3Special” and temper “4” are acceptable for forming cathode cans of theinvention. Other temper designations may be acceptable, for examplewhere the steel composition is correspondingly adjusted. TABLE 1Property Inv. Ex. #1 Inv. Ex. 2 Temper Number 3 Special 4 Grain Size,ASTM E112-88 7-12 9-12 Yield Strength 45-52 ksi 32-45 ksi Elongation,Nm, 80-100 mm width 25% 35% Hardness, Vickers 93-117 93-117 ErichsenDuctility ASTM E643-84 ≦7.5 mm ≦9.5 mm

[0101] The physical properties in TABLE 1 suggest that the metal strip84 of Inv. Ex. #1 should be harder and less formable than theconventional battery grade metal strip illustrated as Inv. Ex. 2. Yetbattery-forming experiments by the inventors herein show that eithermaterial is suitable for making cathode cans, and cells made therewith,using methods disclosed herein.

[0102] The composition of preferred steel layer 60, and as in theexamples indicated in Table 1, is AISI 1008, which is less than 0.1percent by weight carbon. Other steels can be used so long as theysatisfy the above noted formability and strength requirements.

[0103] A significant advantage of the apparatus and processes disclosedherein is that the resulting cathode can has a relatively thicker bottomwall 36 and a relatively thinner side wall 37. Starting with a 0.152 mmthick metal strip, bottom walls of cans made according to the inventionare about 0.152 mm thick, with modest variation.

[0104] By comparison, the stretched and polished or ironed side walls 37are about 0.105 mm thick, reflecting the dimension of the clearancebetween punch and die in the first punch step. Thus, the greaterthickness of the bottom wall benefits the need for thickness to providestrength in the bottom wall, while the lesser thickness in the side wallprovides adequate strength for two reasons. First, the side wall issubjected primarily to in-line stresses that travel along the directionof extension of the side wall. Second, the side wall is strengthened,toughened, such as by hardening, by the working of the metal as the sidewall is thinned.

[0105] By so thinning the side wall, the absolute amount of space takenup by the side wall is reduced, whereby the grommet and anode cans canbe specified with correspondingly larger inner diameters, with theresult that the space occupied by the anode cavity is correspondinglyenlarged. The enlargement of the anode cavity increases the capacity ofthe anode cavity to receive additional electroactive anode material,whereby the electrical watt-hour capacity of the cell is increased.

[0106] A further advantage of the can forming system, and methods, ofthe invention is that the bottom corner of the cathode can is formed bya stretching process, rather than a purely punching, compressiveprocess, whereby there is no tendency for the bottom corner of the canto bulge outwardly. Accordingly, no allowance need be made in thespecification for bulging cans, whereby the specification range for celldiameter can be tightened, toward a larger average diameter, whereby theaverage diameters of the seal and anode can may be increasedaccordingly, thereby to increase the size of the anode cavity. Assuggested earlier, increasing the size of the anode cavity increases theamount of electroactive anodic zinc which can be packed into the cell,resulting in an increase in the absolute amount of useful electricitywhich can be extracted from a cell of a given IEC standard size.

[0107] Materials suitable for use as metal strip 84 include nickelplated steel. The steel layer can be, for example, cold rolled steel,cold rolled mild steel, or stainless steel. Other steels may be used asdesired, so long as they exhibit suitable strength in combination withsuitable forming capabilities. The nickel can be plated or clad onto thesteel core layer. The nickel layers are preferably generally purenickel. However, alloys of nickel are also acceptable, such as INCONEL(INCO alloy of nickel, a non-magnetic alloy); pure nickel with minoralloying elements (NICKEL 200 and related family of NICKEL 200 alloyssuch as NICKEL 201, etc.), all available from Huntington Alloys, adivision of INCO Huntington, W. Va., USA. Some noble metals can alsofind use as plating, cladding etc., including for example, and withoutlimitation, gold, silver, platinum, palladium, and the like.

[0108] Those skilled in the art will now see that certain modificationscan be made to the apparatus and methods herein disclosed with respectto the illustrated embodiments, without departing from the spirit of theinstant invention. And while the invention has been described above withrespect to the preferred embodiments, it will be understood that theinvention is adapted to numerous rearrangements, modifications, andalterations, and all such arrangements, modifications, and alterationsare intended to be within the scope of the appended claims.

[0109] To the extent the following claims use means plus functionlanguage, it is not meant to include there, or in the instantspecification, anything not structurally equivalent to what is shown inthe embodiments disclosed in the specification.

Having thus described the invention, what is claimed is:
 1. A cathodecan comprising a bottom wall, and a circumferential side wall, extendingupwardly from a lower edge of said side wall adjacent said bottom wall,and terminating at an upper, distal edge, said side wall having a heightgenerally corresponding to an overall height of said cathode can of nomore than about 15 mm, and a circumference defining an overall diameterof said cathode can of no more than about 25 mm, the ratio of theoverall height to the overall diameter of said cathode can being about0.1/1 to about 1/1, said side wall having a first strength greater thana second strength of said bottom wall, the strength of said side wallbeing related to the strength of said bottom wall as a side wallhardness of about 130 to about 185 Vickers is related to a bottom wallhardness of about 93 to about 117 Vickers.
 2. A cathode can as in claim1 , the ratio of the strength of said side wall to the strength of saidbottom wall, on the Vickers scale, being between about 0.60/1 and about0.85/1.
 3. A cathode can as in claim 1 wherein the hardness of said sidewall is about 130 to about 185 on the Vickers scale and the hardness ofsaid bottom wall is about 93 to about 117 on the Vickers scale.
 4. Acathode can as in claim 1 , the height of said side wall being no morethan about 8 mm and the overall diameter of said cathode can being nomore than about 15 mm.
 5. A cathode can as in claim 1 , said side wallhaving an outwardly-disposed ironed surface, the outwardly-disposed sidewall surface, as ironed, comprising a first surface finish, said bottomwall having a second surface finish, the surface finish of the side wallbeing related to the surface finish of the bottom wall as a surfacefinish R_(A) of less than 2 microinches is related to a surface finishR_(A) of about 2 microinches to about 5 microinches.
 6. A cathode can asin claim 1 , said bottom wall having a first thickness, said side wallhaving a second thickness no more than about 85 percent as great as thethickness of said bottom wall.
 7. A cathode can as in claim 1 ,comprising first and second layers comprising nickel, and a layer ofsteel between said nickel layers.
 8. A cathode can as in claim 7 , andincluding a metal plating layer on at least one of said nickel layerssuch that the respective nickel layer is between said plating layer andsaid steel layer.
 9. A cathode can as in claim 1 , including at leastone air port in said bottom wall.
 10. A cathode can as in claim 1 , thestructure of said can being representative of a can defined tosubstantially the full height thereof in a single fabrication step. 11.A cathode can as in claim 1 , the structure of said can beingrepresentative of a can fabricated only in steps wherein a punch movestoward a female die.
 12. A cathode can as in claim 1 , the structure ofsaid can being representative of a can defined to substantially the fullheight thereof in a single fabrication step of drawing and ironing,starting from a flat work piece element.
 13. A cathode can as in claim 1, the structure of said can being representative of a can fabricated insteps wherein ironing occurs only in combination with drawing.
 14. Acathode can as in claim 1 , the structure of said can beingrepresentative of a can fabricated using a step wherein ironing isperformed simultaneously over substantially the full height of said sidewall.
 15. An air depolarized electrochemical button cell, comprising:(a) an anode; (b) a cathode including a cathode can, and a cathodeassembly in said cathode can, said cathode can comprising a bottom wall,and a circumferential side wall, extending upwardly from a lower edge ofsaid side wall adjacent said bottom wall, and terminating at an upper,distal edge, the ratio of the overall height to the overall diameter ofsaid cathode can being about 0.1/1 to about 1/1, said side wall having afirst strength greater than a second strength of said bottom wall, thestrength of said side wall being related to the strength of said bottomwall as a side wall hardness of about 130 to about 185 Vickers isrelated to a bottom wall hardness of about 93 to about 117 Vickers; (c)a separator; and (d) an electrolyte. said button cell having an overallheight of no more than about 15 mm and an overall diameter of no morethan about 25 mm.
 16. An air depolarized electrochemical button cell asin claim 15 , the ratio of the strength of said side wall to thestrength of said bottom wall, on the Vickers scale, being between about0.60/1 and about 0.85/1.
 17. An air depolarized electrochemical buttoncell as in claim 15 wherein the hardness of said side wall is about 130to about 185 on the Vickers scale and the hardness of said bottom wallis about 93 to about 117 on the Vickers scale.
 18. An air depolarizedelectrochemical button cell as in claim 15 , the height of said sidewall being no more than about 8 mm and the overall diameter of saidcathode can being no more than about 15 mm.
 19. An air depolarizedelectrochemical button cell as in claim 15 , said side wall having anoutwardly-disposed ironed surface, the outwardly-disposed side wallsurface, as ironed, comprising a first surface finish, said bottom wallhaving a second surface finish, the surface finish of the side wallbeing related to the surface finish of the bottom wall as a surfacefinish R_(A) of less than 2 microinches is related to a surface finishR_(A) of about 2 microinches to about 5 microinches.
 20. An airdepolarized electrochemical button cell as in claim 15 , said bottomwall having a first thickness, said side wall having a second thicknessno more than about 85 percent as great as the thickness of said bottomwall.
 21. An air depolarized electrochemical button cell as in claim 15, comprising first and second layers comprising nickel, and a layer ofsteel between said nickel layers.
 22. An air depolarized electrochemicalbutton cell as in claim 21 and including a metal plating layer on atleast one of said nickel layers such that the respective nickel layer isbetween said plating layer and said steel layer.
 23. An air depolarizedelectrochemical button cell as in claim 15 , including at least one airport in said bottom wall.
 24. An air depolarized electrochemical buttoncell as in claim 16 , the structure of said can being representative ofa can defined to substantially the full height thereof in a singlefabrication step.
 25. An air depolarized electrochemical button cell asin claim 16 , the structure of said can being representative of a canfabricated only in steps wherein a punch moves toward a female die. 26.An air depolarized electrochemical button cell as in claim 16 , thestructure of said can being representative of a can defined tosubstantially the full height thereof in a single fabrication step ofdrawing and ironing, starting from a flat work piece element.
 27. An airdepolarized electrochemical button cell as in claim 16 , the structureof said can being representative of a can fabricated in steps whereinironing occurs only in combination with drawing.
 28. An air depolarizedelectrochemical button cell as in claim 16 , the structure of said canbeing representative of a can fabricated using a step wherein ironing isperformed simultaneously over substantially the full height of said sidewall.
 29. A cathode can having a bottom wall, and a circumferential sidewall, extending upwardly from said bottom wall, said side wall having aheight generally corresponding to an overall height of said cathode canof no more than about 15 mm, and a circumference defining an overalldiameter of said cathode can of no more than about 25 mm, the ratio ofthe overall height to the overall diameter of said cathode can beingabout 0.1/1 to about 1/1, said side wall having an outwardly-disposedironed surface, the side wall surface, as ironed, comprising a firstsurface finish, a corresponding outwardly-disposed surface of saidbottom wall having a second surface finish, the surface finish of theside wall being related to the surface finish of the correspondingoutwardly-disposed surface of the bottom wall as a surface finish R_(A)of less than 2 microinches is related to a surface finish R_(A) rangingfrom about 2 microinches to about 5 microinches.
 30. A cathode can as inclaim 29 , the surface finish of the side wall ranging from about R_(A)0.5 microinch to about R_(A) 1.5 microinches and the surface finish ofthe bottom wall ranging from about R_(A) 2.5 microinches to about 4.5microinches.
 31. A cathode can as in claim 29 , comprising first andsecond layers comprising nickel, and a layer of steel between saidnickel layers.
 32. A cathode can as in claim 29 , the height of saidside wall being no more than about 8 mm and the overall diameter of saidcathode can being no more than about 15 mm.
 33. A cathode can as inclaim 31 , and including a metal plating layer on at least one of saidnickel layers such that the respective nickel layer is between saidplating layer and said steel layer.
 34. A cathode can as in claim 29 ,including at least one air port in said bottom wall.
 35. An airdepolarized electrochemical button cell as in claim 29 , the structureof said can being representative of a can defined to substantially thefull height thereof in a single fabrication step.
 36. An air depolarizedelectrochemical button cell as in claim 29 , the structure of said canbeing representative of a can fabricated only in steps wherein a punchmoves toward a female die.
 37. An air depolarized electrochemical buttoncell as in claim 29 , the structure of said can being representative ofa can defined to substantially the full height thereof in a singlefabrication step of drawing and ironing, starting from a flat work pieceelement.
 38. An air depolarized electrochemical button cell as in claim29 , the structure of said can being representative of a can fabricatedin steps wherein ironing occurs only in combination with drawing.
 39. Anair depolarized electrochemical button cell as in claim 29 , thestructure of said can being representative of a can fabricated using astep wherein ironing is performed simultaneously over substantially thefull height of said side wall.
 40. An air depolarized electrochemicalbutton cell, comprising: (a) an anode; (b) a cathode including a cathodecan, said cathode can having a bottom wall, and a circumferential sidewall, extending upwardly from said bottom wall, the ratio of the overallheight to the overall diameter of said cathode can being about 0.1/1 toabout 1/1, said side wall having an outwardly-disposed ironed surface,the side wall surface, as ironed, comprising a first surface finish, acorresponding outwardly-disposed surface of said bottom wall having asecond surface finish, the surface finish of the side wall being relatedto the surface finish of the corresponding outwardly-disposed surface ofthe bottom wall as a surface finish R_(A) of less than 2 microinches isrelated to a surface finish R_(A) ranging from about 2 microinches toabout 5 microinches; (c) a separator; and (d) an electrolyte, saidbutton cell having an overall height of no more than about 15 mm and anoverall diameter of no more than about 25 mm.
 41. An air depolarizedelectrochemical button cell as in claim 40 , the surface finish of theside wall ranging from about R_(A) 0.5 microinch to about R_(A) 1.5microinches and the surface finish of the bottom wall ranging from aboutR_(A) 2.5 microinches to about 4.5 microinches.
 42. An air depolarizedelectrochemical button cell as in claim 40 , comprising first and secondlayers comprising nickel, and a layer of steel between said nickellayers.
 43. An air depolarized electrochemical button cell as in claim40 , the height of said side wall being no more than about 8 mm and theoverall diameter of said cathode can being no more than about 15 mm. 44.An air depolarized electrochemical button cell as in claim 42 , andincluding a metal plating layer on at least one of said nickel layerssuch that the respective nickel layer is between said plating layer andsaid steel layer.
 45. An air depolarized electrochemical button cell asin claim 40 , including at least one air port in said bottom wall. 46.An air depolarized electrochemical button cell as in claim 40 , thestructure of said can being representative of a can defined tosubstantially the full height thereof in a single fabrication step. 47.An air depolarized electrochemical button cell as in claim 40 , thestructure of said can being representative of a can fabricated only insteps wherein a punch moves toward a female die.
 48. An air depolarizedelectrochemical button cell as in claim 40 , the structure of said canbeing representative of a can defined to substantially the full heightthereof in a single fabrication step of drawing and ironing, startingfrom a flat work piece element.
 49. An air depolarized electrochemicalbutton cell as in claim 40 , the structure of said can beingrepresentative of a can fabricated in steps wherein ironing occurs onlyin combination with drawing.
 50. An air depolarized electrochemicalbutton cell as in claim 40 , the structure of said can beingrepresentative of a can fabricated using a step wherein ironing isperformed simultaneously over substantially the full height of said sidewall.
 51. A method of fabricating a cathode can from a metal striphaving a first thickness between opposing surfaces thereof, using apunch in combination with a female die, the female die comprising aninitializing land, an upstanding inner side wall, a cavity definedinwardly of the inner side wall, and a lip between the initializing landand the inner side wall, and thereby fabricating a cathode can having abottom wall and a side wall, an overall height, and an overall diameter,the method comprising: (a) urging the punch against an element of themetal strip and thus urging both the punch and the metal strip into thecavity in the female die such that the metal strip is disposed between afirst outer surface of a side wall of the punch, and a second innersurface of the side wall of the female die, the metal thus being drawnabout the lip of the female die, the lip of the female die comprising afirst outer cross-sectional radius disposed toward the initializingland, and a second inner cross-sectional radius disposed toward theinner side wall, the first radius being disposed between the secondradius and the initializing land, the second radius being smaller thanthe first radius and being disposed between the first radius and theinner side wall; (b) moving the punch, and the corresponding element ofthe metal strip, into the cavity such that the outer side wall of thepunch comes into facing, and thus working, relationship with the innerside wall of the female die, the clearance between the respective innerand outer side walls being less than the thickness of the metal stripbeing drawn therebetween, whereby movement of the punch into the cavityand corresponding drawing of the metal strip, along with the punch, andinto sliding engagement against the inner surface of the side wallresults in rubbing, surface-to-surface engagement of anoutwardly-disposed surface of the metal strip against correspondingportions of the inner surface of the female die, thus drawing the metalstrip, and working the surface of the metal strip, thereby making acathode can precursor as an integral part of the metal strip, thecathode can precursor having a bottom wall, and a side wall extendingupwardly from the bottom wall; and (c) subsequent to step (b), severingthe cathode can precursor from the metal strip, thereby to form thecathode can.
 52. A method as in claim 51 including, prior to urging thepunch and metal element into the cavity, cutting leading and trailingedges of the element transversely across the strip while retainingattachment of the element to the strip at opposing sides of the strip.53. A method as in claim 51 , the moving of the punch into the cavitythus cold working the metal strip by both thinning the metal and bendingthe metal, such working of the metal strip at the outwardly-disposedsurface thereby increasing the smoothness of the outwardly-disposedsurface of the metal strip.
 54. A method as in claim 51 , the bottomwall of the cathode can precursor having a second thickness, the sidewall of the cathode can precursor having a third thickness, no more thanabout 85 percent as great as the second thickness.
 55. A method as inclaim 51 wherein the metal strip comprises first and second layerscomprising nickel, and a layer of steel between the nickel layers.
 56. Amethod as in claim 51 , further including the step of post-plating thecathode can with a plating material after the severing of the cathodecan precursor from the metal strip, whereby the workedoutwardly-disposed surface is plated with the plating material.
 57. Amethod as in claim 51 wherein the ratio of the second radius to thefirst radius is about 2/1 to about 8/1.
 58. A method as in claim 51wherein the ratio of the second radius to the first radius is about 3/1to about 6/1.
 59. A method as in claim 51 wherein the ratio of thesecond radius to the first radius is about 4/1.
 60. A method as in claim51 , the ratio of the clearance between the punch and the female die tothe thickness of the metal strip, before step (a), being about 0.5/1 toabout 0.85/1.
 61. A method as in claim 51 , the metal strip having ahardness of about 93 to about 117 on the Vickers scale prior to beingworked in said cavity.
 62. A method as in claim 51 , that portion of themetal strip which is cold worked in the cavity having a hardness ofabout 130 to about 185 on the Vickers scale.
 63. A method as in claim 51, including defining substantially the full height of the can in asingle fabrication step.
 64. A method as in claim 51 , includingfabricating the can using only steps wherein a punch moves toward afemale die.
 65. A method as in claim 51 , including definingsubstantially the full height of the can in a single fabrication step ofdrawing and ironing, starting from a flat work piece element.
 66. Amethod as in claim 51 wherein ironing occurs only in combination withdrawing.
 67. A method as in claim 51 wherein ironing is performedsimultaneously over substantially the full height of the side wall. 68.An air depolarized electrochemical button cell comprising an anode, acathode including a cathode can fabricated according to a method ofclaim 51 , a separator, and an electrolyte.
 69. An air depolarizedelectrochemical button cell comprising an anode, a cathode including acathode can fabricated according to a method of claim 52 , a separator,and an electrolyte.
 70. An air depolarized electrochemical button cellcomprising an anode, a cathode including a cathode can fabricatedaccording to a method of claim 53 , a separator, and an electrolyte. 71.An air depolarized electrochemical button cell comprising an anode, acathode including a cathode can fabricated according to a method ofclaim 54 , a separator, and an electrolyte.
 72. An air depolarizedelectrochemical button cell comprising an anode, a cathode including acathode can fabricated according to a method of claim 55 , a separator,and an electrolyte.
 73. An air depolarized electrochemical button cellcomprising an anode, a cathode including a cathode can fabricatedaccording to a method of claim 56 , a separator, and an electrolyte. 74.An air depolarized electrochemical button cell comprising an anode, acathode including a cathode can fabricated according to a method ofclaim 57 , a separator, and an electrolyte.
 75. An air depolarizedelectrochemical button cell comprising an anode, a cathode including acathode can fabricated according to a method of claim 58 , a separator,and an electrolyte.
 76. An air depolarized electrochemical button cellcomprising an anode, a cathode including a cathode can fabricatedaccording to a method of claim 59 , a separator, and an electrolyte. 77.An air depolarized electrochemical button cell comprising an anode, acathode including a cathode can fabricated according to a method ofclaim 60 , a separator, and an electrolyte.
 78. An air depolarizedelectrochemical button cell comprising an anode, a cathode including acathode can fabricated according to a method of claim 61 , a separator,and an electrolyte.
 79. An air depolarized electrochemical button cellcomprising an anode, a cathode including a cathode can fabricatedaccording to a method of claim 62 , a separator, and an electrolyte. 80.An air depolarized electrochemical button cell comprising an anode, acathode including a cathode can fabricated according to a method ofclaim 63 , a separator, and an electrolyte.
 81. An air depolarizedelectrochemical button cell comprising an anode, a cathode including acathode can fabricated according to a method of claim 64 , a separator,and an electrolyte.
 82. An air depolarized electrochemical button cellcomprising an anode, a cathode including a cathode can fabricatedaccording to a method of claim 65 , a separator, and an electrolyte. 83.An air depolarized electrochemical button cell comprising an anode, acathode including a cathode can fabricated according to a method ofclaim 66 , a separator, and an electrolyte.
 84. An air depolarizedelectrochemical button cell comprising an anode, a cathode including acathode can fabricated according to a method of claim 67 , a separator,and an electrolyte.
 85. A can forming system for forming a cathode canfrom metal strip, said can forming system comprising a punch incombination with a female die, and a severing device, said female diecomprising an initializing land, an upstanding inner side wall extendingabout a cavity, and a lip between said initializing land and said innerside wall, said lip of said female die comprising a first outercross-sectional radius disposed toward said initializing land, and asecond inner cross-sectional radius disposed toward said inner sidewall, the first radius being between the second radius and saidinitializing land, the second radius being smaller than the first radiusand being disposed between the first radius and the inner side wall,said severing device severing the cathode can precursor from the metalstrip, thereby to form the cathode can, the cathode can having a bottomwall, at least one air port in the bottom wall, a side wall extendingupwardly from the bottom wall, an overall height, and an overalldiameter.
 86. A can forming system as in claim 85 , and including themetal strip, having a thickness, and, being disposed between said punchand said die as said punch, and the corresponding element of the metalstrip, moves into the cavity such that said outer side wall of saidpunch comes into facing, and thus working, relationship with said innerside wall of said female die, the clearance between respective saidinner and outer side walls being less than the thickness of the metalstrip being drawn therebetween, whereby movement of said punch into thecavity and corresponding drawing of the metal strip, along with thepunch, and into sliding engagement against the inner surface of saidside wall results in rubbing, surface-to-surface engagement of anoutwardly-disposed surface of the metal strip against correspondingportions of the inner surface of said female die, thus drawing the metalstrip and thereby substantially thinning the metal strip and working themetal strip by both substantial thinning of the metal and bending themetal, the drawing, working, and corresponding thinning of the metalstrip giving the outwardly-disposed surface of the metal strip a finersurface finish than the bottom wall, and thereby making a cathode canprecursor as an integral part of the metal strip.
 87. A can formingsystem as in claim 86 , the metal strip comprising first and secondlayers comprising nickel, and a layer of steel between the nickellayers.
 88. A can forming system as in claim 87 , the metal strip havinga hardness of about 93 to about 117 on the Vickers scale prior to beingworked by said can forming system.
 89. A can forming system as in claim88 , that portion of the metal strip which is worked in the can formingsystem having a worked hardness of about 130 to about 185 on the Vickersscale.
 90. A can forming system as in claim 85 , defining substantiallythe full height of the can in a single fabrication step.
 91. A canforming system as in claim 85 , fabricating the can using only stepswherein a punch moves toward a female die.
 92. A can forming system asin claim 85 , defining substantially the full height of the can in asingle fabrication step of drawing and ironing, starting from a flatwork piece element.
 93. A can forming system as in claim 85 whereinironing occurs only in combination with drawing.
 94. A can formingsystem as in claim 85 wherein ironing is performed simultaneously oversubstantially the full height of the side wall.
 95. A cathode can madewith a can forming system of claim 85 , the side wall of the can havinga height generally corresponding to an overall height of the cathode canof no more than about 15 mm, the overall diameter of said cathode canbeing no more than about 25 mm.
 96. A cathode can made with a canforming system of claim 86 , the side wall of the can having a heightgenerally corresponding to an overall height of the cathode can of nomore than about 15 mm, the overall diameter of said cathode can being nomore than about 25 mm.
 97. A cathode can made with a can forming systemof claim 87 , the side wall of the can having a height generallycorresponding to an overall height of the cathode can of no more thanabout 15 mm, the overall diameter of said cathode can being no more thanabout 25 mm.
 98. A cathode can made with a can forming system of claim88 , the side wall of the can having a height generally corresponding toan overall height of the cathode can of no more than about 15 mm, theoverall diameter of said cathode can being no more than about 25 mm. 99.A cathode can made with a can forming system of claim 89 , the side wallof the can having a height generally corresponding to an overall heightof the cathode can of no more than about 15 mm, the overall diameter ofsaid cathode can being no more than about 25 mm.
 100. A cathode can madewith a can forming system of claim 90 , the side wall of the can havinga height generally corresponding to an overall height of the cathode canof no more than about 15 mm, the overall diameter of the cathode canbeing no more than about 25 mm.
 101. A cathode can made with a canforming system of claim 91 , the side wall of the can having a heightgenerally corresponding to an overall height of the cathode can of nomore than about 15 mm, the overall diameter of the cathode can being nomore than about 25 mm.
 102. A cathode can made with a can forming systemof claim 92 , the side wall of the can having a height generallycorresponding to an overall height of the cathode can of no more thanabout 15 mm, the overall diameter of the cathode can being no more thanabout 25 mm.
 103. A cathode can made with a can forming system of claim93 , the side wall of the can having a height generally corresponding toan overall height of the cathode can of no more than about 15 mm, theoverall diameter of the cathode can being no more than about 25 mm. 104.A cathode can made with a can forming system of claim 94 , the side wallof the can having a height generally corresponding to an overall heightof the cathode can of no more than about 15 mm, the overall diameter ofthe cathode can being no more than about 25 mm.